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Palaeogeography, Palaeoclimatology, Palaeoecology
Elsevier
Palaeogeography, Palaeoclimatology, Palaeoecology

Elsevier

0031-0182

Palaeogeography, Palaeoclimatology, Palaeoecology/Journal Palaeogeography, Palaeoclimatology, Palaeoecology
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    Cretaceous (Maastrichtian) chelonian burrows preserved in floodplain deposits in the Bauru Basin of Brazil: Evidence for the fossorial origin of turtle shells

    Silva, Marcio LuizGuedes Silva, Gabriel TeofiloNascimento, Diego LucianoBatezelli, Alessandro...
    12页
    查看更多>>摘要：Burrowing behavior is an important adaptation of animals that live in arid and semi-arid conditions. In this paper, we describe examples of vertebrate burrows from the Upper Cretaceous (Maastrichtian) Adamantina Formation of the Bauru Basin, Brazil, most likely produced by turtles. The Adamantina Formation preserves abundant and diverse turtle body fossils such as Bauruemys elegans (Testudines: Pleurodira); however turtle burrows have not been previously documented. The newly reported burrows are preserved in fluvial sandstone facies and exposed in sections that partially preserve their three-dimensional geometry. Burrows are simple J shaped tunnels with a cross-sectional shape that is semicircular (half-dome) with a flattened floor. Such burrows show a partially preserved entrance with an inclined ramp angle (22 degrees), and grooves and ridges up to 1 cm in width preserved along the burrows walls and floor. The architecture and sedimentary facies of the host sandstone body, together with the occurrence of Taenidium barretti and the absence of rhizoliths, suggest that the burrow was excavated by scratch digging into an exposed point bar of a meandering river channel. Based on burrow morphology, dimensions, as well as ridges,and grooves in the walls and floor, we propose that burrows were formed by a chelonian (such as a freshwater turtle) during aestivation. We highlight that these are first examples of turtle burrows reported from the Cretaceous, and their occurrence reinforces the hypothesis that the original function of turtle shells was as an adaptation to fossorial behavior.
      原文链接:
    • NSTL
    • Elsevier

    Local differences in paleohydrology have stronger influence on plant biomarkers than regional climate change across two Paleogene Laramide Basins, Wyoming, USA

    Azevedo-Schmidt, LaurenDiefendorf, Aaron F.Schlanser, KristenBaczynski, Allison A....
    16页
    查看更多>>摘要：Plant biomarkers in the geologic record are commonly used to reconstruct paleovegetation and paleoclimate. Yet the representativeness of these biomarker-based reconstructions is not entirely straightforward because both local and regional climatic influences are convolved in the recovered biomarker composition. Furthermore, geomorphic processes including sedimentation, deposition, burial rates, and surface and groundwater levels can also influence biomarker preservation and taphonomy. The combination of leaf compression fossils with the biomarker record provides a robust framework in which ecological reconstructions can be made. Herein we present a case study examining the biomarker responses to a major regional climatic signal, the Paleocene Eocene Thermal Maximum (PETM), from local effects in two basins with different paleohydrology: the Hanna Basin (HB) and Bighorn Basin (BHB), in Wyoming (USA). Data collected include (1) leaf wax n-alkanes and plant-derived non-steroidal di- and triterpenoids, (2) pristane/phytane vs. terrestrial to aquatic ratio (Pr/Ph:TAR), plant material source proxy (P-aq), hopanes, and bacteria which provide constraints on organic matter sourcing, redox conditions, and bacterial inputs, and (3) carbon (delta C-13(n-alk)) and hydrogen (delta H-2(n-alk)) isotopic compositions of plant wax n-alkanes. We find the two basins differed significantly in weight % total organic carbon (TOC), alkane and terpenoid concentrations, and delta C-13(n-alk) and delta H-2(n-alk) values. We examined the effects of delta C-13(atm) on delta C-13(n-alk) values by assuming comparable regional climate in the two basins. Differences in paleohydrology and paleovegetation were assessed using the above proxies and previously published paleobotanical data. Local paleohydrologic conditions, an abiotic factor, likely drove variability in plant biomarker preservation and paleovegetation structure. Notably, an abundance of water in the HB during the PETM created a conifer refugium while drying within the BHB caused a local extirpation. This study highlights the importance of considering the influence of local environment, specifically paleohydrology, on the local fossil record and the need to compare multiple sites to disentangle regional climate effects on terrestrial plant communities. Distinguishing local from regional differences is imperative if we are to understand how ecosystems respond to future climate change.
      原文链接:
    • NSTL
    • Elsevier

    Subfossil Coleoptera from Eifel maar sediments as indicators of the environmental evolution in Central Europe over the last 60,000 years

    Britzius, SarahSirocko, Frank
    16页
    查看更多>>摘要：A reconstruction of landscape and paleotemperatures is presented from a composite drill core from the Eifel maar lakes of Auel and Holzmaar, Germany. The compositecore is 112 m long and covers the last 60,000 years (Marine Isotope Stages MIS 3, 2, and 1) based on the new ELSA-20 stratigraphy. Findings are based on an analysis of arthropod remains, with moisture-dependent, riparian or (semi)aquatic Staphylinidae representing the majority of beetle sclerites in the assemblages, especially during cold intervals. Assemblages change corresponding to climate and vegetation, with a greater variety of taxa during the woodland phases (60,000-44,000 yr b2k, i.e. years before 2,000 CE) versus cold adapted taxa during late MIS 3 and early MIS 2 (28,500-23,500 yr b2k). Beetles that inhabit damp, moist or wet locations, as well as aquatic or riparian taxa are present throughout the record. The assemblage corresponding to a period of tundra-like vegetation (29,000-24,000 yr b2k), contained three taxa suitable for temperature calculation (Arpedium brachypterum, Bembidion fellmanni, and Boreaphilus henningianus), all of which are found only in cold phases (Greenland Stadial 2 and 4, and Heinrich Event 2). Paleotemperatures were reconstructed via the Mutual Climatic Range method giving the following results. Mean temperature for the early tundra phase (28,500-27,800 yr b2k) is -32 to -2 ? for the coldest month, and 6 to 9.5 ? for the warmest month. Mean temperature for the later tundra phase (27,000-24,000 yr b2k) is -30 to -20 ? for the coldest month and 6 to 9.5 ? for the warmest month. This shift indicates an increase in seasonality towards the Last Glacial Maximum. Paleotemperature calculations are in good agreement with other European records and indicate a major decline in median winter temperatures towards the Last Glacial Maximum, whereas the summer temperatures remained relatively stable throughout Europe, resulting in an increase in seasonality and continentality.
      原文链接:
    • NSTL
    • Elsevier

    Mineral inputs, paleoecological change, and Holocene carbon accumulation at a boreal peatland in the Hudson Bay Lowlands, Canada

    Da Silva, Kristina A.Snyder, Rebecca A.Packalen, Maara S.McLaughlin, James W....
    12页
    查看更多>>摘要：The Hudson Bay Lowlands (HBL) is a vast contiguous peatland extending over >370,000 km2 in Canada's borealsubarctic, and is the traditional land of the Omushkego Cree. It is currently undergoing climatic warming alongside other anthropogenic stressors, and contains a large below-ground carbon pool. Understanding how climate variability and multiple stressors impact peat accumulation in this region is critical to discerning how northern peatlands will respond to future climate and land-use changes. Pollen- and macrofossil-based paleoecological reconstructions, and analyses of aluminum (Al) and titanium (Ti) fluxes in a Holocene-aged peat core (VM375) taken from a bog in the Attawapiskat watershed were conducted to link ecosystem changes with hydroclimate and long-term carbon storage. Peat initiation is dated to 5780 cal yr B.P., coincident with land emergence driven by glacial isostatic adjustment. From 4500 to 4200 cal yr B.P., apparent rate of carbon accumulation increased, and was linked to more rapid rates of peat accretion and increases in minerotrophic indicators in the pollen record. This increase in peat accretion and shift in vegetation composition co-occur with higher rates of mineral influx as shown by Ti and Al concentrations, which may have supplied nutrients. A fen to bog transition takes place -3300 cal yr B.P., with increases in Sphagnum spores and macrofossils, and a decline in the apparent rate of carbon accumulation relative to the earlier half of the record, where paleoecological proxies indicate treed wetland and fen stages. Since peat inception, the total carbon stock of the 260-cm peat column is 110 kg C m- 2. This multi-proxy record shows an association between changing peat types and variability in apparent rates of carbon accumulation, and supports the hypothesis that mineral nutrients either supplied by surface hydrology or by eolian deposition played a role in Holocene peat carbon accumulation in eastern North American boreal peatlands.
      原文链接:
    • NSTL
    • Elsevier

    Palaeobiogeographical analysis of the Mississippian (early Carboniferous) brachiopod fauna in the Tibetan Plateau

    Qiao, LiZhang, Yi-ChunLiu, Cong-Ying
    8页
    查看更多>>摘要：The Tibetan Plateau comprises several allochthonous terranes/blocks originated from the northern margins of eastern Gondwana. Brachiopod faunas from different terranes were referred either to Gondwana province or Cathaysia province through the Late Palaeozoic. They are very important in studying the palaeobiogeography regarding the early development of the Palaeotethys Ocean. However, due to tectonic complexity and uneven research in fossil groups through time, the palaeobiogeographical connections and geodynamic history of these terranes in the Mississippian (early Carboniferous) remain ambiguous. In this study, the brachiopod dataset was compiled and reviewed at three critical intervals in the Mississippian (Tournaisian, early Vise ' an, and late Vise ' an), based on material from 13 sections in the Tibetan Plateau (the Himalaya, Lhasa, North Qiangtang, and Qamdo) and those from adjacent areas in the Qaidam terrane, Baoshan terrane, Kashmir, Alborz Mountains, and western Australia. We utilized a community detection approach from network theory that incorporates presence-absence patterns of brachiopod genera. The results demonstrated increasing provinciality and endemicity through Tournaisian-Vise ' an, and supported a trend for the North Qiangtang and Qamdo terranes from the transition zone in the Tournaisian and early Vise ' an to a station far from the northern Gondwana margins since the late Vise ' an. This evidence further proves that the Longmu Co-Shuanghu suture zone serves as an effective palaeobiogeographic barrier and represents the main branch of the Palaeotethys Ocean during the Mississippian. The remarkable palaeogeographical reconfiguration represented by the significant palaeobiogeographical frag-mentation appropriately indicates a moderate to low palaeolatitude for the North Qiangtang and Qamdo terranes regarding a persistently widening eastern Palaeotethys Ocean in the late Vise ' an.
      原文链接:
    • NSTL
    • Elsevier

    Pollen R-values in arid central Asia for quantitative palaeo-vegetation reconstruction

    Wang, QiangLi, Jin-FengLu, Kai-QingXie, Gan...
    11页
    查看更多>>摘要：Establishing the relationship between surface pollen assemblages and related modern vegetation provides a bridge for reconstructing the palaeo-vegetation succession and related climate changes. Numerous contributions have demonstrated an inconsistency between the relative abundance values of surface pollen assemblages and corresponding modern vegetation for some taxa, which is attributed to differences in their pollen production, dispersal mode and preservation potential. Consequently, the concept of R-value was introduced as a correction coefficient to counterbalance this discrepancy. Unlike most of the complex forest and grassland ecosystems, desert vegetation with fewer dominant taxa provides a simpler model to demonstrate how to use the R-value to correct this deviation. Here, we propose a scheme of Rrel median values from modern desert vegetation types based on calculated R and Rrel adjustment coefficients of the dominant taxa using surface pollen and related modern vegetation data from 145 sample plots along an east-west desert transect in the eastern arid central Asia (ACA). These data revealed that 1) taking Nitraria as a reference, Chenopodiaceae, Artemisia and Ephedra are highly represented, while Tamaricaceae, Zygophyllaceae, Asteraceae (excluding Artemisia), Calligonum and Poaceae are poorly represented. 2) the pollen representation was constrained by their pollination strategies. For example, anemophilous plants (e.g., Ephedra, Artemisia and Chenopodiaceae) are mostly over-represented, while those of entomophilous taxa (e.g., Nitraria, Tamaricaceae, Zygophyllaceae and Calligonum) are underrepresented. The scheme and findings mentioned above cast a new light on the future of quantitative reconstruction of palaeo-vegetation succession in the ACA.
      原文链接:
    • NSTL
    • Elsevier

    Conifer-mixed tropical rainforest in the Indian Paleogene: New evidences from terpenoid signatures

    Chetia, RimpyMathews, Runcie P.Singh, Prakash K.Sharma, Anupam...
    17页
    查看更多>>摘要：The Paleocene sediments from Barsingsar lignite mine section of Bikaner-Nagaur Basin in Rajasthan, India were subjected to gas chromatography-mass spectrometry (GC-MS) analysis to resolve its botanical history in relation to its terpenoid composition. The terpenoid suite was characterised by sesquiterpenoids, diterpenoids, and sporadic triterpenoids. The presence of sesquiterpenoids along with drimane, norcadalenes, cadalenes and their related compounds hint to higher plant input. High abundance of diterpenoids and their temporal universality imply a significant gymnosperm input. The diterpenoid-class of terpenoids, primarly comprises of conifer-derived abietane, phyllocladane, kaurane, pimarane/isopimarane and podocarpane-class compounds. It further point to Southern Hemisphere conifer families, Podocarpaceae and Araucariaceae. Exceptional void of phenolic abietane and labdane derivatives rule out the probability of Pinaceae as the source of these terpenes. A very low abundance of pentacyclic terpenoids like oleanane-derivatives suggest low angiosperm-derived terpenoid contribution. The average value of pristane/phytane in the realm, 1.7 indicated oxic to suboxic depositional setting. The values of ar-AGI (aromatic Angiosperm/Gymnosperm Index), t-AGI 1 and t-AGI 2 spans over 0.01 to 1, 0.009 to 1.23, and 0.002 to 0.34 respectively for the section. The research provided evidence of the occurrence of a tropical rainforest where conifers were a significant element or remained a refugia in the midst of emerging angiosperms as life stabilized in the Paleogene after the devastating Cretaceous-Paleogene (K/Pg) boundary.
      原文链接:
    • NSTL
    • Elsevier

    Long eccentricity forcing Asian dust input into the northwestern Pacific during the early Pleistocene

    Feng, XuguangJiang, FuqingZhang, ZhaohuiXiong, Zhifang...
    10页
    查看更多>>摘要：Asian dust deposition in the northwestern Pacific is generally linked to high-latitude paleoclimate evolution during the Quaternary. However, whether low-latitude tropical Pacific processes, such as El Nino-Southern Oscillation (ENSO), influence Asian dust input into the northwestern Pacific remains uncertain. Here, we present clear periodic variations in potassium content (K (wt%)) and gamma-ray attenuation (GRA) bulk density, which are closely linked to the variations in Asian dust, in a sediment core recovered at Site U1438 in the Amami Sankaku Basin (ASB), northwestern Philippine Sea. Based on the shipboard age-depth model, we tuned the GRA to the mass accumulation rate curve on the Chinese Loess Plateau and the 8-kyr-lagged obliquity curve, and established the astronomical timescale. The K (wt%) content and GRA were higher during glacials and lower during interglacials, as driven by the variability in the Northern Hemisphere ice sheet (NHIS) during the Quaternary. In addition, strong long eccentricity 405-kyr cycles were observed in the dust records (K (wt%) content and GRA) during the early Pleistocene. The 405-kyr filter results showed that increased (decreased) Asian dust corresponded to the La Nina-like (El Nino-like) state, suggesting that Asian dust input into the northwestern Pacific was modulated by ENSO on 405-kyr cycles in the early Pleistocene. Our study illustrated the possible link between long eccentricity 405-kyr cycles in the Asian interior and low-latitude forcing, including potential modulation by ENSO.
      原文链接:
    • NSTL
    • Elsevier

    A new perspective on Late Eocene and Oligocene vegetation and paleoclimates of South-eastern Australia

    Sluiter, Ian R. K.Holdgate, Guy R.Reichgelt, TammoGreenwood, David R....
    14页
    查看更多>>摘要：We present a composite terrestrial pollen record of latest Eocene through Oligocene (35.5-23 Ma) vegetation and climate change from the Gippsland Basin of south-eastern Australia. Climates were overwhelmingly mesothermic through this time period, with mean annual temperature (MAT) varying between 13 and 18 degrees C, with an average of 16 degrees C. We provide evidence to support a cooling trend through the Eocene-Oligocene Transition (EOT), but also identify three subsequent warming cycles through the Oligocene, leading to more seasonal climates at the termination of the Epoch. One of the warming episodes in the Early Oligocene appears to have also occurred at two other southern hemisphere sites at the Drake Passage as well as off eastern Tasmania, based on recent research. Similarities with sea surface temperature records from modern high southern latitudes which also record similar cycles of warming and cooling, are presented and discussed. Annual precipitation varied between 1200 and 1700 mm/yr, with an average of 1470 mm/yr through the sequence. Notwithstanding the extinction of Nothofagus sg. Brassospora from Australia and some now microthermic humid restricted Podocarpaceae conifer taxa, the rainforest vegetation of lowland south-eastern Australia is reconstructed to have been similar to present day Australian Evergreen Notophyll Vine Forests existing under the sub-tropical Koppen-Geiger climate class Cfa (humid subtropical) for most of the sequence. Short periods of cooler climates, such as occurred through the EOT when MAT was similar to 13 degrees C, may have supported vegetation similar to modern day Evergreen Microphyll Fern Forest. Of potentially greater significance, however, was a warm period in the Early to early Late Oligocene (32-26 Ma) when MAT was 17-18 degrees C, accompanied by small but important increases in Araucariaceae pollen. At this time, Araucarian Notophyll/Microphyll Vine Forest likely occurred regionally.
      原文链接:
    • NSTL
    • Elsevier

    Application of cave monitoring to constrain the value and source of detrital Th-230/Th-232 in speleothem calcite: Implications for U-series geochronology of speleothems

    Wortham, Barbara E.Banner, Jay L.James, Eric W.Edwards, R. Lawrence...
    10页
    查看更多>>摘要：Cave calcite deposits ("speleothems") are widely-used archives of terrestrial paleoclimate signals, in large part because they can be accurately and precisely dated using 238U-series disequilibria (U-series dating) measured by mass spectrometry. Difficulties arise when growth layers in stalagmites incorporate detrital material during calcite deposition that contains significant amounts of 230Th ("detrital 230Th"). U-series ages must be corrected for detrital 230Th either by 1) assuming a detrital 230Th content (expressed as the ratio 230Th/232Th), or by 2) developing isochron models for each stalagmite. We examine two alternative correction approaches for detrital 230Th/232Th: analysis of calcite grown on artificial substrates in central Texas caves (i.e., present-day or "zeroage" calcite) and analysis of soil leachates from the recharge zones of the caves. Samples collected over three years yield elevated detrital atomic 230Th/232Th values, ranging from 5.4 to 28.1 parts per million (ppm) +/- 0.5 ppm (1 sigma uncertainty for a typical measurement), compared with the commonly used "bulk earth" value of 4.4 ppm. Agreement between soil leachate and calcite 230Th/232Th values suggests that soil material is a source of detrital Th in the stalagmites in central Texas. Correlations between Fe, Mn, and Th concentrations in soil leachates from above caves suggests that Th sorbs on to Fe and Mn colloidal material. Independent estimates of detrital 230Th/232Th in a young (< 100 years) stalagmite from central Texas reveal higher 230Th/232Th (-4 to 11 ppm) than bulk earth, consistent with measurements from zero-age calcite and soil (-5 to 20 ppm). These results offer a new method for improving U-series chronologies of stalagmites.
      原文链接:
    • NSTL
    • Elsevier